Objectives: A. Development of a specific material to stimulate calcific closure of the apex in non-vital teeth. B. Application of a specific collagen gel in non-vital teeth of the Rhesus monkey for the purpose of inducing apical closure. Studies undertaken during the year 1974: A. Implantation of polyethylene tubes containing the gel into the subcutaneous connective tissue of Sprague-Dawly rats. Results: The openings of the tubes which had been filled with the gel were occluded by mineralized connective tissue scars. A differentiation of cells into palisading fibroblasts with elaboration of a linear collagen matrix at the tissue-gel interface was an additional interesting finding. B. Prototype study of application of the gel in the devitalized teeth of rhesus monkeys. Results: Radiographic examination of the apices of the teeth indicate apparent calcific closure. Significance of these studies: A. Experiments suggest that this highly purifiable and syringeable gel deposited apically in non-vital open apex teeth may stimulate root end closure. This non-surgical technique may serve to enhance the prognosis and predictability of the treatment in such cases. Research goals for 1975: A. To test this material for efficacy on the non-vital teeth of Rhesus monkeys. B. To determine the practicality of utilizing similar materials in humans.